Impact wrench



IMPACT WRENCH Filed Oct. 18, 19 63 nw aw 5 N, 3 mm N W e 5% m mm 7 0 A M Z J m \v m \w m Kw N Q United States Patent 3,203,283 IMPACT WRENCH John P. Newman, PK). Box 1147, San Jacinto, Calif. Filed Oct. 18, 1963, Ser. No. 317,188 Claims. (Cl. 81-523) This invention relates to a new and improved form of impact wrench.

One of the principal objects of this invention is to provide a power driven impact wrench having novel and improved means for intermittently connecting and disconnecting the driven member from the power driven drive shaft.

Another object of this invention is to provide a power driven impact wrench which is compact in size and of an extremely simple construction permitting an inexpensive and rugged structure.

My U.S. Patent No. 2,733,621 discloses a rotary impact wrench utilizing a resilient sleeve of rubber or rubberlike material which performs the dual functions of storage of energy for the repeated blows or impacts and actuation of the mechanism for intermittently connecting and disconnecting the driver member or anvil from the power driven shaft. While wrenches embodying the invention of said patent and utilizing the cylindrical form of sleeve shown therein have proven to be of great utility, some difiiculties have been encountered in connection with the cylindrical sleeve. That is, under some conditions of heavy usage or load a condition of wear and decreased effectiveness is encountered, due at least in part t chafing or rubbing of the inner surface of the sleeve against the drive shaft. This problem may lead to eventual failure of the sleeve and is cured only in part by the use of lubricants. Also, the cylindrical sleeve must be of appreciable length and this imposes a limitation upon the overall size of the tool, so as to make difficult the design of a tool sufficiently short and compact to meet current user requirements. An important object of the present invention is, therefore, to provide an improved impact wrench structure which is not subject to such disadvantages.

A further object of the present invention is to provide an improved form of resilient sleeve for use in an impact wrench of the type generally described above.

Other objects and advantages of this invention it is believed will be apparent from the following detailed description of a preferred embodiment thereof when read in connection with the accompanying drawings.

In the drawings:

FIGURE 1 is a side elevation, partly in section, of an impact wrench embodying the invention.

FIGURE 2 is a fragmentary side elevation similar to FIGURE 1, but illustrating the hammer in disengaged position.

FIGURE 3 is a sectional view taken substantially on the line 33 of FIGURE 1.

FIGURE 4 is a sectional view taken substantially on the line 4-4 of FIGURE 1.

FIGURE 5 is a fragmentary sectional view similtar to FIGURE 1, but illustrating a modified form of the invention.

Referring now to the drawings, the impact wrench embodying this invention may be provided with an electric motor (not shown) suitably mounted in a housing 11. A downwardly extending handle portion 12 on the housing 11 is proportioned to be received within the palm of the hand by the user, and a trigger element 13 pivotally mounted on the handle portion is adapted to operate a control switch (not shown) for regulating the operation of the electric motor. Electrical current for the motor is transmitted through the cable 14 which depends from the underside of the handle portion 12. A switch lever 15 may also be mounted on the handle 12 for reversing the direction of rotation of the shaft of the motor when desired. It is to be understood that an air driven motor may be substituted for the electric motor if desired, since the particular type of power means employed for turning the drive shaft does not constitute an important part of the invention.

Reduction gearing may be provided for driving the drive shaft 16 from the motor shaft drive gear 17, and as shown in the drawings this gearing may include the pinion gear 18 on the counter shaft 19. A pinion 20 also fixed Ion the counter shaft 19 engages the larger driven gear 21 which is carried on the reduced end 16a of the drive shaft 16. A motor mount and bearing support casting 24 is provided in the housing 11, a suitable bearing assembly 22 for the end 16a of the drive shaft 16 being provided thereon. As shown, the drive shaft is provided with a shoulder member 16b which abut against the face plate of the bearing 22, preventing rearward thrust of the drive shaft.

A housing extension or nose casting 25 is secured at the rearward end thereof to housing 11 by means of bolts 26. The forward projecting end of the housing extension 25 carries a bearing sleeve 28. The drive shaft 16 extends axially through the housing extension 25 and its outer end 29 extends into a bore 27 provided in the driver member 41, which member is supported in the bearing sleeve 28.

A resilient rubber-like driving member or sleeve 30, generally conical in shape, encircles the drive shaft 16 for a portion of the length thereof and is connected at its smaller diameter, forward end in driven relationship with the drive shaft 16 by means of the pin connection 31. The outer ends of the pin 31 extend through a cylindrical reinforcement element or ferrule 32. The rearward, larger diameter end of the sleeve is connected by means of the pins 33 to the rearward end of a hammer member 34 which is rotatably mounted within the housing extension 25. The pins 33 extend through a cylindrical reinforcement element or ferrule 35. A plurality of longitudinal lands 36 are formed, preferably integrally with the housing extension 25 and are provided with cylindrical surfaces 37 so as to function as bearings for the hammer member 34. It will be noted that since the sleeve 30 is constructed of rubber or nibber-like material, the rearward end of the sleeve and hence also the hammer 34 may be driven by the shaft 16 but are capable of relative angular movement with respect thereto.

The hammer 34 is provided at its forward end with a pair of protruding dogs 40 disposed 180 apart. The driver member 41 is rotatably mounted within the bearing sleeve 28 and is provided with a flange portion 42 received within the housing extension 25 and forming an anvil member having a pair of oppositely disposed projections 44, each having radial driving jaw surfaces 45 and 46. From an inspection of FIGURES 1 and 4 it will be apparent that in the normal driving relationship, the dogs 40 contact the respective jaw surfaces 45 of the projections 44.

An adjustment nut 47 is treadedly engaged with the bearing sleeve 28 and is provided with a central opening through which extends the reduced portion 48 of the driver member41, a washer 49 being interposed between the nut 47 and the driver member 41. Means are provided for preventing rearward longitudinal movement of the driver member with respect to the nut 47 while permitting rotational movement of the drivermember with respect thereto, such means comprising a circumferential groove 50 on the portion 48 in which is received a spring retaining washer 51.

The forward end of the driver member 41 is provided with a non-circular portion 52, which ordinarily is formed with a square cross section. A conventional socket member (not shown) provided with a square opening for the reception of the non-circular portion 52 and also provided with the usual socket for the reception of a nut or bolt head is adapted to be retained on the non-circular portion 52.

In operation of the device embodying this invention, the drive shaft 16 is turned by the motor through the reduction gearing described above. So long as no resistance to rotation is imposed by the socket member (not shown), the drive shaft 16, drive sleeve 30, hammer member 34, and drive member 41 all rotate as a unit with respect to the housing extension 25 and bearing sleeve 28. When resistance to rotation of the socket member (not shown) is encountered, such as for example, by the tightening of the nut or bolt (not shown) which is being operated upon, the driver 41 slows down relative to the drive shaft 16. The angular velocity of the hammer 34, it being in driving engagement with the projections 44 of the driver 41, will likewise be reduced. In turn, the speed of rotation of the rearward end of the drive sleeve 30 will be reduced, since it is connected to the rearward end of the hammer 34. However, the forward end of the drive sleeve 30 is rigidly connected to the drive shaft 16 and hence this portion of the sleeve 30 will be rotated at a faster rate of speed than the rearward end thereof. The drive sleeve 30 will accordingly be twisted or placed in torsion an amount dependent upon the degree of relative movement between the hammer 34 and the drive shaft 16.

As the sleeve 30 is twisted the longitudinal dimension thereof increases, causing the rearward end of the sleeve to move relative to the drive shaft 16 and housing extension 24 in a rearward direction, thus also moving the hammer 34 in the same direction. This movement continues until the dogs 40 have been moved out of engagement with the jaw surfaces 45, as shown in FIG- URE 2. At this point, the sleeve 30 is freed of any forces tending to maintain it in torsion, and the energy thereby stored in the sleeve is released, causing the rearward portion of the sleeve to be rotated rapidly at a speed greater than the speed of the drive shaft 16. With the release of this energy the longitudinal dimension of the sleeve 30 is reduced to the original magnitude as shown in FIGURE 1, and the dogs 40 are again engaged with the jaw surfaces 45 of the anvil member. The hammer 34 has a relatively large mass and accordingly, the dogs 40 strike the anvil projections 44 with a sharp blow or impact. Continued resistance to rotation of the socket member (not shown) causes a repetition of the above described cycle of storage of energy in the sleeve 30, disengagement of the hammer from the anvil, release of the energy stored in the sleeve and subsequent engagement of the hammer with the anvil together with the impact therebetween. When the socket member (not shown) is engaged in tightening a nut or bolt, the effect is to apply two separate impacts for each revolution of the drive shaft 16. When the nut reaches its final tightened position, the socket member and driver 41 cease to rotate at all with the result that the hammer 34 comes to a stop and accelerates rapidly twice during each revolution of the drive shaft 16.

If it is desired to remove a tightened nut from a bolt, or if it is desired to tighten a nut having left-hand threads, the direction of rotation of the motor shaft is reversed by means of the switch 15, and in such cases the jaw surfaces 46 on the driver 41 becomes operative. The action of the rubber-like sleeve 30 is the same, however, with the exception that the sleeve is twisted in the opposite direction.

The magnitude of the individual impacts transmitted to the driver 41 may be varied by adjusting the position of the adjustment nut 47 relative to the housing extension 25. This in turn causes a change in the longitudinal position of the driver 41 and the. anvil portion 42 relative to the hammer 34. It will thus be understood that by turning the nut 47 to move it forwardly or rearwardly with respect to the housing extension 25, the longitudinal amount of surface contact between the dogs 40 and the jaw surfaces 45 (or jaw surfaces 46, as the case may be) may be respectively increased or reduced. If a greater magnitude of impact is desired, the nut 47 and its related parts are moved in a rearward direction relative to the housing extension 25, thus providing a greater longitudinal surface contact between the dogs 40 and jaw surfaces 45. Accordingly, a greater amount of twisting of the sleeve 30 is required in order to cause an elongation of the sleeve sufficient to move the dogs out of contact with the jaw surfaces 45. Therefore, a greater amount of energy is stored in the sleeve 30 causing a greater impact. If, on the other hand, a lesser impact is desired, the nut 47 is moved forwardly with respect to the housing extension 25 and a smaller longitudinal surface contact between the dogs 40 and jaw surfaces 45 is provided, ultimately resulting in a lesser impact.

The conical shape of the sleeve 30 is greatly superior to the cylindrical shape of the sleeve shown in the abovementioned patent in that it is incapable of being twisted in such a way as to result in any chafing or rubbing contact with the drive shaft 16 during operation of the device. Thus, maximum driving power is obtained without excessive wear or weakening of the sleeve. Moreover, the conical configuration results in a sleeve of shorter length, thus permitting design of an appreciably shorter tool with the resulting advantages in ease of handling and use.

A modified form of the invention is shown in FIGURE 5. This structure is the same as that shown in FIGURES 1 through 4 and described above, with the exception that the conical sleeve 30 is provided with an annular bead or projection 60 adjacent the rearward, larger diameter end of the sleeve on the inner surface thereof. Positioned forwardly of this bead is a bearing member 61 having a central bore 62 and a generally conical outer surface 63 conforming to the inner surface of the sleeve 30 and in contact therewith. It will thus be understood that the bead 60 acts to retain the bearing member 61 in place, the head 60 being sufficiently resilient to permit insertion of the bearing member in an end-wise direction during assembly of the parts.

In use, the bearing member 61 has two functions: It serves to prevent any tendency of the sleeve to collapse inwardly as it is twisted to the position shown in FIG- URE 2, and also, the bearing member functions as a bearing for the rearward end portion of the hammer 34, the bearing member rotating with the sleeve and hammer during operation. The forward portion of the hammer 34 bears against the ferrule 32. If desired, in this embodiment,'the bearing surfaces 37 can be dispensed with.

Preferably, the bearing member 61 is made of nylon or light material, and if desired may be made up of a plurality of washer-like segments.

Having fully described the invention, it is to be understood that it is not intended to limit the invention to the details herein set forth, but it is of the full scope of the appended claims.

I claim:

1. In an impact wrench, the combination of a drive shaft, a driver member mounted coaxially of the drive shaft, power means for rotating the drive shaft, a hammer member rotatably mounted coaxially of the drive shaft, a conical shaped resilient driving member coaxial with said drive shaft, said driving member having conical inner and outer surfaces and a small diameter end and a large diameter end, said driving member being operably connected to the hammer for rotation therewith and driven from the drive shaft, cooperating means on said hammer member and said driver member for releasable engagement therebetween, means for connecting to the,

hammer member the large diameter end of the resilient driving member, said large diameter end being most remote from the cooperating means as compared to said small diameter end, and other means for connecting the small diameter end of the resilient driving member to the drive shaft so that upon relative rotational movement between the hammer member and the drive shaft the resilient driving member is twisted and thereby elongated to move the hammer member out of engagement with the driver member.

2. The combination of claim 1, including means for adjusting the position of the hammer member relative to the driver member.

3. The combination of claim 1, wherein the cooperating means comprises radial jaw faces on said hammer member and said driver member.

4. In an impact wrench, the combination of a drive shaft, a driver member mounted coaxially of the drive shaft, power means for rotating the drive shaft, a hammer member rotatably mounted coaxially of the drive shaft, a conical-shaped resilient driving member coaxial with said drive shaft, said driving member having conical inner and outer surfaces and a small diameter end and a large diameter end, said driving member being operatively connected to the hammer for rotation therewith and driven from the drive shaft, a bearing member having a conical outer surface disposed between said driving member and said drive shaft, the conical surface of said bearing member conforming to and being in contact with the inner conical surface of said driving member, cooperating means on said hammer member and said driver member for releasable engagement therebetween, means for connecting to the hammer member the large diameter end of the resilient driving member, said large diameter end being most remote from the cooperating means as compared to said small diameter end, and other means for connecting the small diameter end of the resilient driving member to the drive shaft so that upon relative rotational movement between the hammer member and the drive shaft the resilient driving member is twisted and thereby 6 elongated to move the hammer member out of engagement with the driver member.

5. In an impact wrench, the combination of a drive shaft, a driver member mounted coaxially of the drive shaft, power means for rotating the drive shaft, a hammer member rotatably mounted coaxially of the drive shaft, a conical-shaped resilient driving member coaxial with said drive shaft, said driving member having conical inner and outer surfaces and a small diameter end and a large diameter end, said driving member being operatively connected to the hammer for rotation therewith and driven from the drive shaft, a bearing member having a conical outer surface disposed between said driving member and said drive shaft, the conical surface of said bearing member conforming to and being in contact with the inner conical surface of said driving member, the inner surface of said driving member being provided with an annular bead at the rearward end thereof for retention of said bearing member in the assembled condition, cooperating means on said hammer member and said driver member for releasable engagement therebetween, means for connecting to the hammer member the large diameter end of the resilient driving member, said large diameter end being most remote from the cooperating means as compared to said small diameter end, and other means for connecting the small diameter end of the resilient driving member to the drive shaft so that upon relative rotational movement between the hammer member and the drive shaft the resilient driving member is twisted and thereby elongated to move the hammer member out of engagement with the drive member.

References Cited by the Examiner UNITED STATES PATENTS 2,733,621 '2/56 Newman 81--52.3

WILLIAM FELDMAN, Primary Examiner. MILTON MEHR, Examiner 

1. IN AN IMPACT WRENCH, THE COMBINATION OF A DRIVE SHAFT, A DRIVER MEMBER MOUNTED COAXIALLY OF THE DRIVE SHAFT, POWER MEANS FOR ROTATING THE DRIVE SHAFT, A HAMMER MEMBER ROTATABLY MOUNTED COAXIALLY OF THE DRIVE SHAFT, A CONICAL SHAPED RESILIENT DRIVING MEMBER COAXIAL WITH SAID DRIVE SHAFT, SAID DRIVING MEMBER HAVING CONCIAL IN NER AND OUTER SURFACES AND A SMALL DIAMETER END AND A LARGE DIAMETER END, SAID DRIVING MEMBER BEING OPERABLY CONNECTED TO THE HAMMER FOR ROTATION THEREWITH AND DRIVEN FROM THE DRIVE SHAFT, COOPERATING MEANS ON SAID HAMMER MEMBER AND SAID DRIVER MEMBER FOR RELEASABLE ENGAGEMENT THEREBETWEEN, MEANS FOR CONNECTING TO THE HAMMER MEMBER THE LARGE DIAMETER END OF THE RESILIENT DRIVING MEMBER, SAID LARGE DIAMETER END BEING MOST REMOTE FROM THE COOPERATING MEANS AS COMPARED TO SAID SMALL DIAMETER END, AND OTHER MEANS FOR CONNECTING THE SMALLL DIAMETER END OF THE RESILENT DRIVING MEMBER TO THE DRIVE SHAFT SO THAT UPON RELATIVE ROTATIONAL MOVEMENT BETWEEN THE HAMMER MEMBER AND THE DRIVE SHAFT THE RESILIENT DRIVING MEMBER IS TWISTED AND THEREBY ELONGATED TO MOVE THE HAMMER MEMBER OUT OF ENGAGMENT WITH THE DRIVER MEMBER.. 